A single-walled carbon nanotube (SW-CNT) is a nano-meter scale tube formed by a cylindrical shell of single atomic layer of carbon atoms. Nanotubes have diameter of a few nm and lengths up to 100 μm so that they form extremely thin wires. The atomic structure of SW-CNT can be formed by wrapping a strip of single atomic layer of graphite sheet along a certain direction. This direction determines the diameter and chirality of the nanotubes.
Experimental and theoretical studies have demonstrated interesting properties from nano-meter sized CNTs have novel electronic properties, which can be metallic or semiconducting, depending on their radius or chiralities.
During manufacture, SW-CNT's include a mixture of metallic and semiconducting nanotubes, thus being difficult to handle. Thus, the nanotubes have been randomly dispersed during the preparations of transistors, diodes, and the like. Application of nanotubes in electronics requires selected types of nanotubes, for example, use of SW-CNT's as transistor channels requires semiconducting SW-CNT's while use of SW-CNT's as conductors for on-chip interconnects requires metallic SW-CNT's. A controlled method of reliably placing and sorting nanotubes is desired.